A 10-square mile solar project designed to provide electricity to San Diego might not feature its signature mirrored dishes if it ever gets built.

Developer Tessera Solar said Wednesday it has sold the project, known as Imperial Valley Solar to a company that specializes in more traditional photovoltaics.

Tessera has run into financial and legal hurdles in building the 709-megawatt project, most of which is on federal land near Plaster City.

It referred questions to the buyer, Arlington, Va.-based AES Solar, a joint venture between AES Corporation and Riverstone Holdings.

Patty Rollin, a spokeswoman for AES, wouldn't talk about the company's plans. "Thank you for your interest," she wrote in an e-mail. "We do not comment on projects under development."

The project is under a legal cloud.

The Quechan Indian tribe last year sued to block the project, claiming it had not been properly consulted. A San Diego judge granted a preliminary injunction against construction.

Other groups have also sued, claiming permits were improperly issued and the project will cause unwarranted environmental damage.

At the same time, Tessera said it didn't have the money to build the project, which would cost $2 billion.

A sister company, Stirling Energy Systems, was working on developing the thousands of mirrored dishes to collect heat from the sun and convert it to electricity using Stirling engines.

Both Tessera and Stirling are owned by NTR, a money-losing Irish conglomerate that wrote off millions that it had invested in the projects and the technology before looking for buyers.

NTR said Thursday that it has delayed deployment of the Stirling dishes while it looks for someone with money and the capability to manufacture them.

In a statement, Jim Barry, the company's chief executive, didn't disclose the terms of the transaction, but implied NTR continues to have an interest in the project.

"I am very pleased that the Imperial Valley Solar Project will be brought to the next phase of development by AES Solar," he said. "They have a significant pedigree in developing solar projects and through their efforts, we are confident that the value created by Tessera Solar in this project will be enhanced for NTR shareholders over time."

It's unclear what technology AES plans to use, but another big Stirling project in San Bernardino County was converted to more traditional photovoltaics after Tessera sold it in December.

Unlike Stirling engines, which use the sun's heat to make electricity, photovoltaics use sunlight.

Up to now, AES Solar has focused on photovoltaic projects. It runs a number of solar farms in Europe, according to its website, and has a "pipeline" in places, like California, where governments subsidize solar production.

Its goal, it said, is to develop photovoltaic projects cheaply enough that they can compete with conventional sources of electricity.

San Diego Gas & Electric has a 20-year contract to buy 300 megawatts from the project beginning in December 2012, and options for more power. A megawatt is enough for about 650 homes.

She said she doesn't know AES's plans for the project, but said the SDG&E will work with the owners. She said the utility is counting on power from the solar farm and all its contracts remain in place.

SDG&E and other big California utilities are making deals for power from wind, solar and geothermal plants. They are working to meet a state requirement that they get a third of the power they sell from renewable sources by 2020.